The present invention relates to valve action in relation to an internal combustion engine in automobiles and, more particularly, to a desmodromic valve actuation system for intake and exhaust function of a four-stroke piston in such engines.
Valve action of internal combustion engines is required to control the piston chamber for four functions of intake, compression, combustion and exhaust. The proper timing for opening and closing these valves is extremely critical to effectively and efficiently produce the horsepower for an internal combustion engines. The standard method of controlling and operating these cams is initiated by a timing belt that connects the engine crankshaft to a camshaft. The camshaft has a series of cams, one for each intake and exhaust valve in each cylinder. The cams, as presently configured in all four cycle engines, are designed to displace the valve inwardly to open either the intake port or the exhaust port. The cams are incapable of closing the port openings; and, accordingly, springs, that are compressed when the cams open a port, are energized to provide forces that close the port. The energy merely supplies the force to return the valve to closed position when the energy is released, but the cam provides control of the valve. This control is necessary so that acceleration/deceleration of the valve can be accomplished with minimum impact loading of the valve seat and hence minimize noise. Further, the frequency of cycles for opening and closing of the valve is quite high requiring very high spring loading to accelerate the mass of the valve.
The four-cycle internal combustion engine requires a first cycle that is the intake wherein a mixture of gas and air enters an opened valve intake port. The piston is displaced vertically down the piston cylinder by the engine crankshaft. The second cycle is compression of the gas/air mixture. The piston is driven up the cylinder by the crankshaft. Both intake and exhaust valves are in a closed position to effectively seal the piston cavity and allow the pressurization of the gas/air mixture. At the appropriate time a spark is introduced to the mixture and an explosion occurs with rapid expansion of the resulting gases. The piston is driven down by the force of the expanding gas which in turn applies a resultant torque to the crankshaft. This torque when combined with a sequence of these explosions at additional pistons will result in the rotational energy of the engine and in its output horsepower. The final cycle is the return up the cylinder by the piston wherein the exhaust valve port is opened and allows gases to escape. At the conclusion of this cycle the next series of cycles is ready to commence by the intake cycle. It can be seen that the valve""s closing and opening are essential in the process along with their control in the speed of their action and the duration they remain closed. It is desirable to operate these valves at the highest speed possible for effective and efficient power generation.
The opening of the valves by the camshaft is a positive mechanical operation by the individual cams. The closing of the valve is a kinematic action resulting from the energy stored in the spring to return and close the valve. This complete function severely limits the speed at which the engine can run, as the valve mass inertia is critical for the stored energy of the spring and limits the cycle time. The acceleration and deceleration of the cam for high cycling conditions can severely limit the size of the spring.
The normal function in the automobile engine is such that there is a firing sequence for the cyclinders that are constantly repeatable regardless of whether the car is parked or moving at any speed. Accordingly, the same displacement of gas/air mixture is constantly used regardless of speed or stopped. It can be seen that, when stopped, the engine uses much more gas than necessary, when all that is required is to keep the engine running can be accomplished with very minimal amounts of air/gasoline mixture. Power is required for accelerating a vehicle which requires richer mixtures and higher speeds of the engine. If the valves can be controlled during acceleration, efficient and effective volumes of mixture can be ingested in the cylinder for the appropriate condition of speed, thereby offering fuel economy. Finally, when achieving a desired speed it is only necessary to overcome the wind drag forces, the friction of the wheels on the road and the internal friction of the drive train and engine inertia to maintain the velocity. This can be accomplished with less than the total displacement put out by the engine. It would be desirable for effective gas consumption to have the ability to not only control the amount of air/gas mixture entering each piston but also have the ability to close any number of cylinders while the engine is performing with the remaining operational cylinders. Of necessity, the timing is critical for the closing down and reopening of the selected cylinders that become inoperative.
It is, therefore, the object of the present invention to provide means that will significantly reduce gas consumption of an internal combustion engine as typically found in an automobile by efficiently and effectively controlling valve port openness in concert with the requirements of the operation of a vehicle.
It is yet another object of the invention to present the means by which valve control is simple, precise and timely, which in turn will be in concert with the engine performance and results in immediate smooth sensitive control of the engine performance and in turn the automobile.
It is an additional object of the invention to provide the means for the necessary timing of the valve in a piston to be in sequence and in position relative to port opening and closing as well as acceleration and deceleration requirements of the valve.
It is also an object of the invention to present the means by which piston firing sequences and individual operations will be designed and controlled.
It is a further object of the present invention to provide a valve control system that is simplified in nature but more effective in controlling the percentage opening of valve ports and will completely eliminate the necessity of springs in the functioning of valves as found in present-day automotive internal combustion engines.
It is another object of the invention to provide a valve actuation system that will be considerably amenable to higher engine speed performance, enhancing the engine performance with resulting savings of gasoline.
It is a further object of the present invention to provide a simple robust construction of a valve actuator that is simple in operation and precisely controlled at all times.
These and other objects are well met by the presently disclosed effective, highly efficient, essentially springless (desmodromic) and substantially infinitely variable valve actuator system of this invention for use with, for example, an internal combustion engine. In one aspect of the invention a first action of a linearly reciprocating actuation system by a rotating cam and translating means interacts with a second controllable actuating means that controls valve position, and will be substantially infinitely variable in displacement thereby controlling the percentage of port opening in each piston separately or in unison. Any percentage opening of the valve port is achievable to the extent that the valve port can be closed indefinitely all the while the engine is performing under the influence of the remaining operating pistons. All the control exercised on the valves are performed easily, quickly and in total concert with the continuous smooth operation of the engine. All these functions can be computer controlled as a function of vehicle performance and will not affect the smoothness of operation of the internal combustion engine and in turn the vehicle itself.
In an embodiment of the invention, a reciprocating cam translating device is coupled to a rotary cam which receives an input from, for example, a pulley driven by a timing belt from an output shaft of an internal combustion engine. A second device, under controlled conditions, converts the reciprocating linear motion at the reciprocating cam translating device into a substantially infinitely variable reciprocating motion, which, in fact, is the valve itself. The rotary cam having a grooved track in a circular flat disk, with appropriate configuration, displaces a translating means which is a ball constrained in a slide which, in turn, reciprocates in a slot to achieve the first reciprocating linear movement. Attached to the slide is an assembly that contains a rotable link in which a slot of appropriate length and juxtaposition such that as the assemblage translates in accordance to the reciprocation of the first device along its line of action the slot presents an angle to that line. Pins affixed to the valve will ride in the slot and the valve, fixed in the engine block will move up and down as the slot reciprocates in accordance with the first cam/translating means. The up and down movement of the valve is dependent on the angle the slot makes with the line of action of the first translating means. A repeatable fixed point in the slot is required no matter what the angle is and as it will repeatably define the closed position of the valve regardless of how much opening of the port is required. If the link is rotated to where the centerline is co-axial with the line of action the valve has closed the port and will remain closed while the engine is still performing. Rotation of the link is performed by an adjustable member which has a slot parallel to the line of action that allows a pin, which rotates the link to any angle, to slide along the line of action and at the same time secures the angular position of the slot. This adjustable slide must move normal to the line of action in a housing affixed to the engine block. Control of the adjustable slide by an actuator, electromechanical or hydraulic, with position information of the slide will effectively control rotation of the link and in turn the amount of port opening.
The cam groove curvatures are shown such that the proper rise and fall along with dwell time are in concert with the engine. The rise and fall cam curvature can be of any variationxe2x80x94linear, spiral, sinusoidal or desired algebraic polynominal. Curvatures ideally should be such that significant effort should be exercised to use as long a time as possible to decelerate and land the valve as easily as possible to reduce landing click.
In another aspect of the invention computer control of each valve allows operation of any set of pistons such that for, preferably, an eight cylinder engine 2, 4, 6 or 8 pistons (although the invention is not limited to a specific number of cylinders) could be operating at any time while those that are operating have the further enhancement of variable valve displacement. Under the most economic conditions while stopped six cylinders could be non-functional while two cylinders with minimal valve openings would be sufficient to keep the motor running. Under computer control while accelerating, the required number of pistons and valve opening percentages will be functioning. At the required cruising speed the minimal number of pistons and most economical valve port opening will be in effect. There are any number of variations on how to control these valves. One controller could control all the valves at once with no ability to turn off any piston. Two controllers where one controls two pistons and the other controls four pistons. This gives the option of two, four or six pistons working. The ideal would be one controller for each cylinder.
For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying drawings and detailed description and its scope will be pointed out in the appended claims.